The invention relates to the field of video chroma-key process and more particularly to such a process requiring "master" and "slave" video cameras wherein the conventional procedure is for the master video camera to focus upon live action whereas the slave camera focuses on a static display or set which may be to a different dimensional scale from the live action. One such process is described in my above-identified U.S. Pat. No. 4,092,673. Another such process is detailed in the patent to Van Slater U.S. Pat. No. 3,914,540, issued Oct. 21, 1975 and entitled "Optical Node Correcting Circuit". In both processes the movement of the video cameras which are focused on the live scene and on the static display must be synchronized in all motions. The basic video camera motions, like the cinema camera motions, are described as dollying, trucking, panning, tilting and camera lens zooming. Dollying and trucking relate to the movement of the camera pedestal longitudinally and transversely. Panning refers to a rotation of the camera itself about a vertical axis. Tilting refers to the rotation of the camera about horizontal axis. The present invention is related to the camera motions known as panning and tilting.
In the conventional video camera the incoming light is dispersed to red, green and blue receptors by means of a prism placed in the path of the lens axis. Heretofore, it was necessary to either electronically or mechanically compensate for the fact that in both pan and tilt operations of the conventional video camera the pivot axes for these motions have been off-axis from that optical point in the video camera defined by the intersection of the lens axis with the receptor axes of the color sensors, designated "the vertex".
Therefore the relative scale of the master camera set to the slave camera set has had to be a factor in determining the individual tilt and pan of the two cameras, since a "lever arm" motion is involved in either pan or tilt motion when the tilt or pan axis is removed from the point of optimum pivot set forth above. If the mounts on the pedestals for both cameras for a chroma-key process, such as that described in the above-mentioned previous patents, are such that the pan axis passes through the described coincidence point in the lens axis and the tilt axis passes through that same point, then no mathmatical adjustment is necessary if both of the cameras are equally tilted or panned on the camera mount.
The instant invention provides means for achieving simultaneous tilt and pan motions of two linked cameras without mathematically derived correstions for scale in a camera support within which the cameras may be mounted to correlate the tilt and pan pivot axes with the camera intersection point for camera lens and color receptor axes.